Guys,
Forgive me for
beating a dead horse about torsionals. I have been reading another list
for (VAF and RV-7) ~2 years, and have anxiously anticipated installing a 13B,
and now instead a Renesis engine, in my soon-to-start RV-7. Now, I am
hearing things that cause me to question my ability to make a sound decision
in this regard, as this is the first discussion of torsionals is the first I
have heard. I am beginning to question my ability to follow through on
what I had taken to be the best alternative engine
choice.
I am therefore
forwarding the most seemingly competent post (I am not enough of an engineer
to evaluate this) regarding this issue. My first impressions were that
rotaries were much less susceptible to torisionals that regular engines, but
recently that view has come into apparently serious question, based on the
statements below.
Appreciate your
thoughts and comments.
Regards,
Greg
Fuess
Greg, I believe the best evidence
that Bill's viewpoint is somewhat misleading is that there are very few
powersport PSRUs flying - while between the old Ross RSRU and Tracy's
series of Redrives there has to be at least 30 airfames flying. Tracy
has over 1400 hours, many others are in the hundreds of hours and one
gyrocopter (Using a Ross Planetary PSRU reported had accumulated over 2500
hours) with not a single reported case (to my knowledge) of PSRU failure
caused by torsional problems. My point is that if there were a problem
with torsionals and the planetary gear box approach to PSRUs for the
rotary it would have surfaced long before now.
I think someone pointed out that
there is a difference in the load profile between a dyno and a propeller -
perhaps that could be the reason these "Failures" only seem to happen on
Dynos.
However, having said that - YOU are
the one that has to make the decision. You are doing the right thing in
getting different viewpoints - but, viewpoints and opinions are cheap.
Evidence of what is working in aircraft, I believe is what you should look
for. The PowerSport PSRU will apparently work, even if a big heavy and
pricey, and we know that Tracy's redives work with numerous flying
examples. But, you need to consider your comfort level with
each.
Good luck
Ed
Anderson